For half a century, writes a Mansfield, O., correspondent of The Cincinnati Commercial Gazette, D. M. Cook bas boen a familiar figuro in Richland county, and bas been marked for his singular inventivo genius. In 1850, when a youug man, he becanie impressed with the wonders of electrical scienoe, and tlicn became onaniored of its study. He began to deive into the unknown of tliis bidden force, and for thirty-six years in alternately brilliant and adverse circumstancos has troddcn over this field till there is no nook or corner with which lic is unacquainted. He ( omnienced his studies at a timo when 1 ttle was known of electricity, and by a pursult of knowledge in that direction with uubounded zeal, he has not only kept apace with tho wizards of the day, but has so far gotten in advance of them that his assertions are aliuost accepted as altogether Incrédulo fis. But no matter whether his claims Beem wonderful and almost beyond belief, they are worthy of credonce, for lic must bc placed in tho list of succes8ful inventors. In 1852 he conceived and constructed a device that revoluUonized the mauufacture of sorgbum sirup. The device was called an evaporator, and was used to niake sirup from sorghum. His principie w:is to run tlie juice across a heated surfacc in zig-zagrows till the juiee would run out as a pure sirup ready for the table, the water being evaporated in ils passage, and the impurities being tLrown lo ono side. On this he reoeived letters patent in 1858, and in 18.39 a company began the manufacture of the same. Thousands and thousand were dispposed of, varying in price from $25 to f35, over $4,000,000 being realized, on which the inventor got a bandsome royalty. Through this he derived quite a fortune, although a portion of it he spent in improving and introducing the deviee. Eren to th s day a fivm in Cincinnati is engaged in the manufacture of this same evaporator, from which the members of t he lirm made themselves rich. ('ook, however, several years ago lost his right to the royalty by some means or other, and bas not been drawing anything from that souroe since. Save for this slight diversion. Mr. Cook has not experimenteel in any field outside of electricity since tbirty-eight yeara ago to any considerable extent, but in this direction he can be said to have spent the greater part of bis life. For a while he sought to solve the question of cheap power, l'ght, etc, bv prodneing the proper current by means of a battery. He invented a battery of peculiar valué for teiegrapb parposes, wbich was in use for a loag time at Crestline, on the Western Union, and until the discovery of the cheap gravity battery that is now in use. Bul Mr. Cook long ago concluded in his own mind thnt in dynaiuic electrieity lay future success. Accordingly be cast asiile the battery as a secondary afl'air, and set about lo experiment with dynainos of novel and peculiar construct or. For several years past be would occaslonally meet me and speak of bis discoveries in the electrical field, but would say that he had not yet secured the resul ts he was after. He would teil me: "When I get my experimenta completed 1 want to show you what will revolulionize the world. I propose to make a perpetual electric generator or motor wliicb will propei itselt by its own current, the resistance of the generator proper being only about 10 per cent. of the rotary power of the electric engine upon wbich the current of the generator aots. " This assertion was sufïicient to shock an ordinary person's nerves, but I accepted the statement witli much allowanco. However, I became intorested and kept watcliing results. Last November Mr. Cook camo to me and said: "I have at last met with success. I have found the principie that I have been hunting for so long. I can now start a dynamo togoing, and it will never stop except by the wvaring away of ts own parts. Ñot only will it run itself by its own current, but also produce power enongh, according to the size of the engine, to run auy machine in the world. 'Perpetual motion," I suggested. "More tbau that," be replied. "It is perpetual motion with only 10 per cent of the force nsed, leaving 90 per cent for power to be utilized as is desired. ïiot only that, but more; one helix of my dynamo will produee light in proportion to its size wbile the other is making the current that runs the engine. It will serve to l.eatyour house, so that instead of having1 stoves and grates, littlis wires will run through your rooms, and on your parlor table wül be a highly burnished apparatus containing w re?, etc, wbich will keep tho temperaturo of the house at wluitever point you wish. " "What will be the cost to run it?" "Nothing. As 1 said, start it, and it 'will go. Heat, power, and light produced by one machine, for absolutely nothing." I looked at him to sec if hewas tliere yet, and if so, whether he was mail, in earnesl. or joking. He laughed at my astonishment, and said: "I am now mak'mga model, and when far enough along I will sliw it to you." The matter was not specially discussed after that, although he would frequcntly bring up the question, until a day or two ago, and I bad serious doubts whether he would ever show the device to me. I thought of Keely and his motor, and feit that the results Mr. Cook professed bimself able to obuün were such that be would keep secret his machine, if he had any, in order to mystify the public. My surprise may be imagined, therefore, when Mr. Cook carne to me a few days ago and said: "I believe I will show you my electric engine and generator. I am far enough along now to show you how the results are accomplished." A time was fixed, and at the appointed hour Mr. Cook called and took me to his farm, about three miles south of Mansfield. As an excuse for a heavy erop of weeds in a fine field, where hundreds of bushels of wheat sbould have been harvestcd, he explained: "I have been so busy with my researches that I have been unable to put out any crops. I could get nobody to altend to the farm, and therefore itis abarren waste. I succeeded in getting a few acres of oats plantod, and that, with a small potato patch, will be all I derive this ycar from this fine traer." Hcre he lives, as he has lived for years, with a wife and 14-year-old daugbter and his wife's sister. Tho. latter is his enthusiastie assistant, and bas helpcd him in many long years of toil. Dislant from tlie house stands an old shop, wherein is hiddeu the secrets of his life. No stranger ever eniers here, for it is herein tliat are con■.íáned the results of tlnrty-six years of iabor. This seclusive rule has been almost invariable, havin been broken but half a dozen times id over a third of a century. Several electricians and two or three others of known integrity havo been admitted, butonly after signing an ironclad agreement not torercnl, patent, or cause to be patented or improved without his consent any of the parts shown to them. The shop is dilapidated, as is the rest of the farm, so much is his mind taken up in the pursuits of his studies. The rear is used as a shelter for his trusty oíd horse, who has done near thirty years of royal service, while the front part is devoted altogether to his laboratory. The agreement signed, Mr. Cook led the way to the door, but before unlocking it grasped me by the hand and had me renew the promise made in the written agreement Thig done, I was ushered into the mysterious room. I was bew.ldered by the appearance of the place. The room was large, aml everywhero hung bundlcs of Wire. Magncts of all snapes and sizes hung abonl the walls and wcre scattered on the Hoor in confused heaps. In one corner was a hiige machine, with largo coils and masjnets, which Mr. Cook told me was the first machine he attempted to make. But in the center of the room sat the pride of his life. 1 saw at a glance that this mysterious miin had not waisted his time and fortune. He had branchcd out from the beaten track, and had produced a machine that d fl'ered in all respests from dynamos of pressnt constrnction, except n that he also used wire anti iron. "This," gak] he, "is iny perpetual electric generator and engine. I will cali my assistant and show you how it works." The machine was rudely constrticted, for Mr. Cock made it all himself wiih a I few oíd tools that liad done too mach service already. Parts of it werc atnde of wood, and the whole was not put together in a very artislic marnier, but it demonstrated his discover)es, and that was his only purpose in i's construction. This model weighs three hundred pounds, and Mr. Cook said by the hand-power of one man could be generated cuirent sufficient to liglit np from thirty to nfty sixtcen caudle-power iucaudescent lainps. His assistant having arrived, wlio by the way is a young lady of hundsome appearance, the work of demonstration began. I testud the current in Beveral ways and foimd it very powcrfiil. Having made electricity somewhat of h. study, I was surprised at the simplieity of many of the principies. The manm r in which he experts to get the reáults heretofore mentioned is theoreticaHy correct, and thur; is 110 mechanical difficulty which he has not already overeóme. After examining the machine carefully in all it.s paits, I was conducted to an adjoining room, where, on a table, sat a smaller model of more accurate make. It contained a much better arrangement of the parU, and from what ho told me I am compclled to belicve all that Mr. Cook had told me. I asked him why he had not sought capita! to develop his tlieories more rapully, when he replied that he had not heretofore been ready. He said: "I wanted to complete my labor.i, so that I conlil say my work is done. I desired to give to (he world a machine perfect in every particular, that would sottle forevermore the question of cheap power, light, and heat. Üp to now my work was not linished. 1 am now alniost done. Within a very short time I shall be able to show to all mankind that 1 have a machine thal will revolutionize the world. When I can exhibit a running model, which 1 can in a few days, then I will be ready to considcr the many propositions that I have already received."